The present invention relates generally to intravascular devices used in magnetic resonance imaging. More particularly, the present invention relates to a ceramic reinforcement member for reinforcing elongated intravascular magnetic resonance imaging devices.
Tracking of catheters and other devices positioned within a body may be achieved by means of a magnetic resonance imaging (MRI) system. Typically, such a magnetic resonance imaging system may be comprised of a magnet, a pulsed magnetic field gradient generator, a transmitter for electromagnetic waves in radio frequency (RF), a radio frequency receiver, and a controller. In a common implementation, an antenna is disposed either on the device to be tracked or on a guidewire or a catheter (commonly referred to as a magnetic resonance catheter or an MR catheter) used to assist in the delivery of the device to its destination. In one known implementation, the antenna comprises an electrically conductive coil that is coupled to a pair of elongated electrical conductors that are electrically insulated from each other, and that together comprise a transmission line adapted to transmit the detected signal to the RF receiver.
In one embodiment, the coil is arranged in a solenoid configuration. A patient is placed into or proximate the magnet and the device is inserted into the patient. The magnetic resonance imaging system generates electromagnetic waves in radio frequency and magnetic field gradient pulses that are transmitted into the patient and that induce a resonant response signal from selected nuclear spins within the patient. This response signal induces current in the coil of electrically conductive wire attached to the device. The coil thus detects the change of status of the nuclear spins in the vicinity of the coil. The transmission line transmits the detected response signal to the radio frequency receiver, which processes it and then stores it with the controller. This is repeated in three orthogonal directions. The gradients cause the frequency of the detected signal to be directly proportional to the position of the radio-frequency coil along each applied gradient.
The position of the radio frequency coil inside the patient may therefore be calculated by processing the data using Fourier transformations so that a positional picture of the coil is achieved. In one implementation, this positional picture is superposed with a magnetic resonance image of the region of interest. This picture of the region may be taken and stored at the same time as the positional picture or at any earlier time.
Elongated intravascular devices utilized in association with MRI applications must generally be made from low magnetic susceptible materials, otherwise they will disturb the magnetic resonance (MR) image of the surrounding body tissue. It is not uncommon for elongated intravascular devices, such as catheters and guidewires, to utilize a reinforcement mechanism so as to enable particular desired mechanical characteristics, such as a desired tensile strength or desired features related to flexibility. It is therefore necessary, within the context of MRI-related applications, that reinforcement mechanisms within elongated intravascular devices be made from low magnetic susceptible materials.
Presently, it is not uncommon for an elongated intravascular member, such as a catheter or a guidewire, to incorporate a strand of reinforcement material, or a layer of braided or woven reinforcement material, into a coaxial layer of the elongated member. In non-MRI applications, strands, wires and/or fibers incorporated into these types of reinforcement mechanisms can be constructed of highly magnetic materials such as stainless steel. In many instances, highly magnetic materials demonstrate desirable mechanical characteristics (i.e., a desirable tensile strength, flexibility, etc.) In MRI applications, however, to avoid interference with magnetically generated images, such highly magnetic materials are typically replaced with lower magnetic metals or special alloys (like Tantalum, Elgiloy, MP35N, etc.). In the context of MRI applications, however, all metal materials and metal alloy materials will still have some negative influence on the magnetic image.
In some instances, polymer fibers which have, of course, no negative influence on the magnetic image have been incorporated into elongated intravascular MRI devices for reinforcement. Polymer fibers, however, as compared to the metal and metal alloy materials, have generally inferior mechanical qualities.
The present invention addresses at least one of these and other problems and offers advantages over the prior art.
The present invention generally pertains to elongated intravascular MRI devices adapted to be advanced through a vessel of a subject. In particular, the present invention provides one or more constructions of such intravascular devices that incorporate reinforcement mechanisms that enable both desirable mechanical qualities and minimal negative magnetic interference with MR imaging.
One embodiment of the present invention pertains to a reinforced magnetic resonance imaging catheter. The catheter comprises an elongated body having at least one lumen extending therethrough. The elongated body also includes a proximal end, a distal end, a circumference, a longitudinal axis running between the proximal and distal ends, and a coaxial layer that incorporates at least one elongated ceramic member. An antenna is operably disposed proximate the distal end of the elongated body.
Another embodiment of the present invention pertains to an elongated medical device for intravascular manipulation during magnetic resonance imaging of body tissue. The device includes an elongated body and a reinforcement mechanism disposed about a portion of the elongated body. The reinforcement mechanism comprises at least one elongated ceramic member.
Another embodiment of the present invention pertains to a reinforcement member for reinforcing an elongated intravascular magnetic resonance imaging device. The reinforcement member comprises an elongated ceramic fiber and a coating disposed about the elongated ceramic fiber.
These and various other features, as well as advantages which characterize the present invention, will be apparent upon a reading of the following detailed description and review of the associated drawings.